The present invention relates to a method for setting one or more virtual volume groups in a storage network system.
A technique of virtual hardware has advanced. This technique allows a user to use hardware that is not actually present in an apparatus as if this hardware were present in the apparatus.
It is assumed that a first apparatus has a virtual device and a second apparatus has a physically existing device (thereinafter, called “physical device”). To apply the virtual technique to these apparatuses, a link is typically established therebetween, so that a user can access the physical device through the virtual device. Once receiving a request for using the virtual device from a user through a user terminal, the first apparatus enables the user to utilize the physical device via the link. In this case, the first apparatus serves as an intermediate between the user terminal and the second apparatus.
Referring to FIG. 15A, a storage apparatus R1 uses physical volumes of a storage apparatus R2 as virtual volumes. The storage apparatus R2 has three physical (or real) volumes (LUs 5, 6 and 7). The storage apparatus R1 uses two of them (LUs 5 and 6) as virtual volumes, and enables a user to use the storage apparatus R2 as if the virtual volumes were stored in the storage apparatus R1. The storage apparatus R1 integrates the virtual volumes into a single volume group AG 1. Note that this volume group is constituted by a bundle of virtual volumes integrated in accordance with conditions of a computer.
When the virtual volume group is created, the virtual volumes are not always integrated into a large single volume group, but the size of the virtual volume group can be determined flexibly depending on an application. To give an example, Japanese Unexamined Patent Application Publication 2004-178253 discloses a method for integrating the volumes, depending on disk specifications such as the type of a disk or the level of Redundant Arrays of Inexpensive Disks (RAID), when virtual volumes are created.
However, in conventional techniques, physical and virtual volumes are not distinguished from each other. This may be advantageous for some applications, but in general, the distinction is essential to make full use of hardware characteristics, such as achieving load distribution.
Referring to FIG. 15B, four virtual volumes (LUs 5, 6, 7 and 8) are allocated to two physical disks in the storage apparatus R2. The storage apparatus R1 integrates virtual volumes into the two volume groups (AGs 3 and 4).
The real volumes to be linked by the virtual volumes (LUs 5 and 6) of the AG 3 are allocated to the single disk, whereas the real volumes corresponding to the virtual volumes (LUs 7 and 8) of the AG 4 are allocated to the different disks. Accordingly, it is assumed that two processes are assigned to the volume groups AGs 3 and 4, respectively. In this state, if the volume groups AGs 3 and 4 are used at the same time, then load distribution cannot be achieved. This is because the LUs 5, 6 and 7 are present in the single physical disk.
This disadvantage is due to the fact that the volume groups are not set based on the arrangement of the real volumes in each physical disk. As in the above conventional techniques, when the volume groups are set based on disk specifications such as the type of disk or the level of the RAID, information on physical disks cannot be obtained. Accordingly, when the volume groups are assigned to real volumes, the virtual volumes with a heavy load may be assigned to the real volumes in the single physical disk. Consequently, the access is prone to be concentrated on the single physical disk, thereby deteriorating the access capability of the system composed of the storage apparatuses.